1. Field Of the Invention
The present invention is directed to a therapy apparatus for treatment with focused acoustic waves of the type having a source of acoustic waves which generates acoustic waves focused onto a focus, an x-ray locating system for locating a region to be treated in a subject with which the subject can be transilluminated from different directions, a central ray of the locating beam assuming, in a common plane, a first direction for a first irradiation direction and a second direction for a second irradiation direction, and a positioning device for adjusting the subject and the focus relative to one another, such that the region to be treated is located in the focus of acoustic waves in the way required for the therapy.
2. Description of the Prior Art
Such therapy systems are suitable, for example, for the treatment of stone conditions (lithotripsy), for treating tumors or for treating bone conditions (osteorestoration). In the first instance, a shock wave source is usually provided as the source of acoustic waves. In the case of tumor treatment, for example, a pressure pulse source that generates negative pressure pulses (under-pressure) and/or an ultrasound source that emits continuous ultrasound (hyperthermia) can be provided as the source of acoustic waves. A shockwave source is likewise normally provided as the source of acoustic waves for treating bone conditions.
In therapy systems of the type initially described (see, for example, European Application 0 405 282), the positioning device is normally and adjustment system with which the region to be treated and the focus are adjustable relative to one another in a first adjustment direction that usually perpendicularly intersects the plane containing the central ray of the locating beam. Moreover, the adjustment device usually permits adjustment in a second direction as well as a third adjustment direction, which are selected such that the region to be treated and the focus are adjustable relative to one another in the plane of the central ray. The three adjustment directions thereby usually proceed parallel to the axes of a rectangular (Cartesian) coordinate system.
For positioning a region to be treated in the focus, one usually proceeds by first irradiating the subject to be treated with the x-ray locating means in the first irradiation direction and the region to be treated is brought into the plane of the central ray by movement in the first adjustment direction. By movement in the second adjustment direction, care is subsequently exercised to insure that the region to be treated lies on the central ray proceeding in the first direction. The x-ray locating means is now pivoted and the subject to be treated is irradiated from the second transillumination direction. For adjustment in the third adjustment direction, which proceeds parallel to the first direction assumed by the central ray in the first irradiation direction, care is exercised to insure that the region to be treated comes to lie on the central ray proceeding in the second direction. When this is the case, the region to be treated is located in that point through which the central ray proceeds in the first direction as well as in the second direction, and in which the focus of the acoustic waves is also located. The treatment can then be begun.
It can be expedient for various reasons, for example, anatomical reasons, to select the first and second irradiation directions such that neither of the second nor the third adjustment directions proceeds parallel to the first direction or to the second direction of the central ray. When this is the case, it is not possible to bring the region to be treated into the focus in the above-described way on the basis of a single adjustment in the third adjustment direction. This can only be accomplished in an iterative sequence on the basis of repeated changing between the first and second irradiation directions. This is an undesirable condition in clinical practice since, first, the subject to be treated is exposed to an unnecessarily high radiation dose and, second, the locating event becomes extremely complicated.